Mendez strike leaves Arsenal's European hopes hanging by a thread

Given that Arsène Wenger is a staunch advocate of the theory that two-leg European ties are decided by the outcome of the first 90 minutes, it should be considered that Arsenal's Champions League campaign is now hanging by the thinnest of threads. Their first defeat in this competition on Dutch soil, secured by Edison Mendez's 30-yard drive, means that nothing less than victory by two goals, or on penalties, will suffice at the Emirates Stadium two weeks today.

"From tonight we're in a tricky situation because we'll have to score two goals without conceding," Wenger admitted, "but I feel from the game we have seen tonight we have enough confidence and belief that we can achieve that."

The Arsenal manager's faith stems from a first-half performance that ought to have sealed the Gunners' passage to the quarter-finals. Their superiority was unmistakable but their profligacy proved costly. This morning marks the end of Eindhoven's four-day annual carnival but, had Arsenal taken their chances, all the celebrations would have been theirs. "It's a problem of maturity and mental patience," Wenger added. "It is important to continue to attack without making mistakes. We attacked less well in the second half and made a mistake and we were punished. We face that problem every week."

Being forced to overturn a deficit in the return will hold little fear for Arsenal - they have come from behind to force results at home on 12 occasions this season and PSV have scored only three goals on their travels in two seasons of European football. But the current Arsenal side have yet to face a task of this magnitude.

PSV were depleted by the loss of their top scorer, Jefferson Farfán, because of a swollen left foot but his presence would have provided little assistance to a PSV side who spent almost the entire first half defending. Wenger had criticised the PSV manager, Ronald Koeman, for employing "negative" tactics when Arsenal twice drew with his Ajax side in the 2002-03 competition and the Frenchman was frustrated again last night.

"I felt that they started the game to play a nil-nil. It was important to score the first goal and afterwards they defended even more," he said. Koeman rejected Wenger's claim and said: "It was a deserved result and we are in a fantastic position."

At 20.7sec Gilberto Silva's opener when these sides met here in 2002 remains the quickest goal in Champions League history and, though Arsenal did not begin quite as rapidly this time, their slick passing quickly silenced the home crowd. Their fluidity stemmed largely from Tomas Rosicky on the left and PSV had great difficulty handling his linkup play with Cesc Fábregas. The Czech combined neatly with Thierry Henry after 13 minutes and only a strong hand from PSV's Brazilian goalkeeper Heurelho Gomes and a clearance off the line by Carlos Salcido prevented Arsenal from taking the lead. Wenger will have been frustrated that his team failed to capitalise on their dominance as PSV were confined to speculative efforts from long range.

Gomes was again alert when Henry spun and volleyed after 42 minutes before, on the stroke of half-time, one of his trademark curling efforts sailed narrowly wide. PSV showed more endeavour after the interval and Arouna Koné's volley wide from Salcido's deep cross after 53 minutes was a warning for an Arsenal defence which had not been tested until then.

As an attacking unit the Premiership team then retreated into their shells. "What happened in the second half is difficult to say," Wenger said, appearing as bemused as everyone else.

Their earlier misses were duly punished. Shortly after the hour Koné fed Mendez and, with an absurd amount of time and space, he drilled low beyond Jens Lehmann's right arm. It was harsh on Arsenal but it was self-inflicted; Gilberto had temporarily neglected his holding midfield position and, in a similar way to Denny Landzaat for Wigan earlier this month, the Ecuadorian midfielder capitalised with a fine right-foot strike.

On 69 minutes Rosicky and Fábregas exchanged passes but Gomes met the Spaniard's shot with a superb diving save. He was on hand to thwart an Emmanuel Adebayor header soon afterwards and remained unbeaten, despite a fizzing Julio Baptista free-kick late on.

Koeman will return to London in a fortnight with happy memories - he scored the only goal as Barcelona beat Sampdoria in the 1992 European Cup final at Wembley - and unless Arsenal can produce a comeback of the tallest order, he will emerge victorious once more.